There has been much interest in preserving the quality of food products such as fruits, vegetables, meats, dairy products, juices, beverages and the like during storage and shipping. Most of these processes have focused on reducing microorganism growth, for example by using a variety of techniques such as radiation processing, heat sterilization or pasteurization, chemical treatment, or cold storage.
Some types of produce are subjected to radiation such as gamma radiation or ultraviolet radiation to sanitize or sterilize food products. While these processes can destroy the growth of microorganisms in produce, drawbacks of using these types of radiation include breakdown or decomposition of the food products causing off tastes, and off odors. There is also a common public perception that produce treated by radiation may be unsafe for consumption. In addition, gamma radiation and to a lesser extent ultraviolet radiation can be hazardous to biological organisms including humans, and thus general public or household use of such types of radiation is either not possible or unadvisable.
Heat pasteurization and sterilization or has been used for a long time to reduce microorganism growth in many types of produce. Usually the produce is heat pasteurized to extend the shelf-life of the product prior to being sold to the consumer. Heat pasteurization of produce requires substantial energy in order to raise the temperature of the produce to a level suitable to kill microorganisms that can be responsible for the degradation of quality in foods. Further, many products such as fruits and vegetables cannot be treated by heat sterilization or pasteurization without severely affecting the quality of the produce.
Documents have been published regarding the processing of foods to extend shelf life. For example, U.S. Pat. No. 6,010,727 discloses a process for sanitizing fresh foods and beverage products using multiple stages of exposure to wavelengths of ultraviolet, near infrared and infrared light. A food or beverage product is exposed to ultraviolet light to kill microorganisms on the product. However, the UV light damages the organoleptic properties of the product. The damaged organoleptic properties are subsequently restored by exposure of the product to near infrared light. In addition the reference teaches that infrared light may be used to inactivate enzymes responsible for decomposition of the product. A drawback of this reference is that produce must be treated with a plurality of light sources in a complex method. In particular, the produce must be treated with ultraviolet light. In many cases, it is undesirable to treat fresh produce such as fruits and vegetables with ultraviolet light as such treatment can affect the quality of the produce.
The article “The Pasteurization Effect of Laser Infrared Irradiation on Beer” MBAA TQ Volume 38, Number 4, 211-214 (2001) by Vladimir Vasilenko discloses the use of low power, near infrared radiation for pasteurization of beer. However the results indicate that a substantial amount of bacteria remain viable after treatment and the author states that “further improvement is necessary”.
One of the best known methods to extend the quality of produce is by refrigeration. It is well known that refrigeration reduces the metabolic activity of microorganisms and generally slows normal biological and biochemical processes. While it is well known in the art to store fresh produce and other products in refrigerators, most conventional refrigerators are only capable of extending the quality of produce by a short time. Thus, there is a need in the art to further preserve the quality of perishable products during storage or shipping at room temperature, and at reduced temperatures.
It is an object of the invention to overcome disadvantages of the prior art.
The above object is met by the combinations of features of the main claims, the sub-claims disclose further advantageous embodiments of the invention.